DETROIT (Reuters) - Vehicles with small, turbocharged engines do not have a significant edge over larger, more traditional powertrains and in some cases the newer models are slower and less fuel-efficient, Consumer Reports said on Tuesday.

The influential magazine's findings pose a potential obstacle for automakers, which are relying on this relatively new and expensive technology to meet stringent global fuel economy standards over the next several years.

Of the models tested by Consumer Reports, Ford Motor Co's <F.N> Fusion mid-size sedan was among the worst performers. The Fusion with a 2-liter, turbocharged engine got 22 miles per gallon and accelerated to 60 miles per hour in 7.4 seconds.

By contrast, the Honda <7267.T> Accord sedan with a 3.5-liter, six-cylinder engine got 26 miles per gallon and accelerated in 6.3 seconds, according to Consumer Reports.

"If you look at the V-6s, they're a full second faster and yet they're getting quite a bit better fuel economy too -- and these are large, old-school, traditional powertrains," said Jake Fisher, director of auto testing for Consumer Reports.

Turbocharged versions of the Hyundai <005380.KS> Sonata and Kia <000270.KS> Optima sedans also fared worse than the Accord, although their performance was overall better than the Fusion.

Consumer Reports also found that turbocharged models often fell short of fuel economy estimates supplied by the U.S. Environmental Protection Agency -- sometimes by as much as 4 miles per gallon as in the case of the 2.0-liter Fusion -- although the testing methods were different.

Ford, in particular, has been one of the most vocal advocates for this technology. Ford introduced its EcoBoost turbocharged engine in 2009 and will offer that engine in more than 90 percent of models sold in North America this year.

Ford, the second-largest U.S. automaker, has said its models equipped with EcoBoost engines have saved as much as 20 percent in fuel compared with their larger predecessors.

"We cannot answer for how Consumer Reports tested the Fusion, but its findings are not consistent with our internal and external feedback," Ford spokesman Wes Sherwood said.

A SPOTTY RECORD

Vehicles with turbocharged gas engines will account for 70 percent of the U.S. new light vehicle market by 2021, up from less than 10 percent in 2010, Barclays Capital predicted in a research note last year.

Turbochargers work by pushing air more quickly through an engine's combustion chambers than is normally possible, creating more power and potentially boosting fuel economy by at least 5 percent.

BorgWarner Inc <BWA.N> and Honeywell Inc <HON.N> are two of the biggest suppliers of this technology.

Consumer Reports said its tests over the last two years show the turbochargers have a spotty record compared with older technologies in terms of fuel economy and power.

Ford's 1.6-liter, turbocharged Fusion achieved 25 miles per gallon and accelerated to 60 miles per hour in 8.9 seconds, Consumer Reports said. This compares to the 2.5-liter, four-cylinder Toyota <7203.T> Camry, which got 27 miles per gallon and accelerated in 7.7 seconds.

The 1.4-liter turbocharged version of General Motors Co's <GM.N> Chevrolet Cruze compact car is seven-tenths of a second faster than the 1.8-liter, four cylinder version. But both got 26 miles per gallon, instead of the expected 28 mpg for the juiced-up Cruze and 27 mpg for the 1.8-liter version.

Discrepancies between the fuel economy seen by the EPA and Consumer Reports may be due in part to different testing standards. The EPA's highway testing is conducted at an average of 48 miles per hour with a top speed of 60 miles. The magazine drives cars on a stretch of highway at 65 miles per hour.